Trickle film

Investigation of the Behavior of a (Semi-Industrial) Trickle Film, Countercurrent Cooling Tower... 

Heat and Mass Transfer at Countercurrent Trickle Films in a Vertical Channel and a Cooling Tower... 

The process is designed as a dynamic layer crystallization. The heart of the experimental equipment is an autoclave which is mounted in a way that its incline can be adjusted between 0 and 90 degrees (see Figure 6). An important feature are four 35 mm diameter windows, which allow to observe the beginning and the end of the trickling film on the crystallization device (see Figure 7). It was necessary to divide the crystallization surface into six parallel channels,... 

When deriving the methods for calculating the dynamic liquid hold-up, it is assumed that the liquid hold-up is only associated with the trickle film in the random or structured packing. It is also assumed that there are no droplets in the packing and the liquid sprays are also associated with the trickle film. 

There are 3 forces acting upon the hquid trickle films in packed columns gravitational force Kg, viscosity force K, and resistance force K,, [ 12, 19,21,22,58]. The gravitational force can always be regarded as a driving force. Depending on the two other forces K,[, and K, there are two possible ranges [12,19,22) ... 

Further models for determining the liquid hold-up can be found in literature [7, 12, 13-15, 20, 21, 22, 42, 42-44, 58]. The work of Gelbe [22] contains some fundamental considerations on the liquid hold-up, and his work was used as a basis for studies by Reichelt [1], Blafi and Kurtz [42] Mersmann and Deixler [44], as well as a publication by Stein [58], in which he presents new models of straight tubes and structured channels , based on trickle film flow. 

A portion of the effluent is recirculated, ia order to smooth out flow, keep the food concentration constant, lower film thickness and control psychoda flies, and reseed the appHed sewage with acclimatized organisms. The psychoda, or filter fly is a very small iasect that breeds ia thick trickling-filter slimes. It does not bite, but can be a nuisance. Its radius of flight is small, but it can be carried great distances by the wiad. The fly can be controlled ia the development phase by occasional flooding of the filter or chlorination of the appHed sewage. 

R Liquid film flowing over solid particles with air present, trickle bed reactors, fixed bed... 

Some contrasting characteristics of the main lands of three-phase reactors are summarized in Table 23-15. In trickle bed reactors both phases usually flow down, the liquid as a film over the packing. In flooded reactors, the gas and hquid flow upward through a fixed oed. Slurry reactors keep the solids in suspension mechanically the overflow may be a clear liquid or a slurry, and the gas disengages from the... 

Gas-liquid contactors may be operated either by way of gas bubble dispersion into liquid or droplet dispersion in gas phase, while thin film reactors, i.e. packed columns and trickle beds are not suitable for solid formation due... 

In the first class, the particles form a fixed bed, and the fluid phases may be in either cocurrent or countercurrent flow. Two different flow patterns are of interest, trickle flow and bubble flow. In trickle-flow reactors, the liquid flows as a film over the particle surface, and the gas forms a continuous phase. In bubble-flow reactors, the liquid holdup is higher, and the gas forms a discontinuous, bubbling phase. 

In trickle-flow operation, the liquid phase flows downwards, and may or may not cover the solid particles as a film. The gaseous phase moves in either co- or countercurrent, continuous flow. 

GL 16] ]R 12] ]P 15] Using a simple thin-film model for mass transfer, values for the overall mass transfer coefficient were determined for both micro-channel processing and laboratory trickle-bed reactors [11]. The value for micro-reactor processing (fCL = 5-15 s ) exceeds the performance of the laboratory tool Ki a = 0.01-0.08 s ) [11, 12], However, more energy has to be spent for that purpose (see the next section). 

There are a few other kinds of industrial plants. An air-lift tower fermenter was developed by ICI for the production of single-cell protein from methanol which employs an external loop for heat removal. Trickle beds for the treatment of waste waters employ packing structures or packing elements of 4-6 cm dia and porosities above 50%. Microbial films are formed on the packing that react with the organic substrate and the air as the liquid flows down and the air up. 

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